Abstract Low velocity impact (LVI) has always been a potential threaten to composite structures. This out-of-plane dynamic impact load easily leads to a dramatic increase of the strain state in the material transverse plane, which can affect the dynamic stress state and damage evolution of the composite laminate, especially for LVI with a relatively high energy. However, the strain rate effect was always neglected in existing investigations, thus introducing inevitable errors in numerical predictions for engineering practices. To accurately capture the failure process of composite laminates under LVI, a three-dimensional strain-rate-dependent damage model was proposed. This model was composed of three parts: a modified stress–strain relationship for composites under a dynamic stress state; a strain-rate-dependent progressive damage model to evaluate the intra-laminar damage; and a cohesive zone model to examine the inter-laminar delamination. LVI tests with different impact energies were conducted to provide validating data. It is shown that the numerical results from the strain-rate-dependent damage model are highly consistent with the experimental outcomes. The contact force history curves, intra- and inter-laminar damage evolution process are found to be strain rate dependent, and thus the numerical errors predicted by the strain-rate-independent damage model significantly increase with the increment of the applied impact energy, which is unacceptable in practice for LVI with relatively high impact energies.
Abstract Among the various mechanisms which occur during impact, the strain rate effect plays a significant role on the mechanical response of layered carbon fibre reinforced polymer structure. In this work, the viscoelastic behaviour of the material is studied to introduce a strain-rate dependency. To preserve numerical efficiency the generalised Maxwell model, formulated in the strain-space, is taken as a basis. The non-linear viscoelastic behaviour is introduced by coupling the generalised Ma...
Abstract This paper is concerned with the development and validation of a consistency elasto-viscoplastic damage model that accounts for the strain rate-dependent plastic response and the progressive post-failure behaviour of composite materials. The model proposed is suitable for progressive failure analysis of composite materials and structures subjected to loadings at various strain rates. A strain rate-dependent yield criterion is adopted; whereas the standard Kuhn–Tucker conditions for plas...
Last. Xuejie Zhang(TJU: Tianjin University)H-Index: 6
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Abstract Carbon fiber reinforced polymer (CFRP) has been extensively used to strengthen structures owing to its outstanding mechanical properties. With an increasing threat from terrorist bombing attacks and accidental explosions, the application of CFRP has been extended to mitigate the effect of blast loading on structures. A better understanding of the dynamic material properties of CFRP/epoxy laminates at high strain rates is therefore needed for more reliable analysis and design of CFRP str...
A new material degradation model only with fundamental material properties required is proposed for composite progressive damage analysis based on micromechanics. For different failure modes, the effects of fiber and/or matrix damage on the composite material properties are explored, from which the material degradation factors for these failure modes are deduced. The material degradation model is then implemented for progressive damage analyses, using user subroutines in the commercial code ABAQ...
#2Adam Sobey(University of Southampton)H-Index: 11
Last. R.A. Shenoi(University of Southampton)H-Index: 34
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Top-hat stiffened plates provide an efficient structure for engineering applications. During service debonding between the stiffener and the plate is often observed and parametric studies of open section stiffeners have shown that debond size and location have a significant effect on the damage mode of the panel. However, these studies do not consider the interaction of failure modes and do not assess the ultimate failure of the structure. In this paper top-hat stiffened composite structures are...
Low-velocity impact damage can drastically reduce the residual strength of a composite structure even when the damage is barely visible. The ability to computationally predict the extent of damage and compression-after-impact (CAI) strength of a composite structure can potentially lead to the exploration of a larger design space without incurring significant time and cost penalties. A high-fidelity three-dimensional composite damage model, to predict both low-velocity impact damage and CAI stren...
Abstract We investigate dynamic fracture of three types of multiwalled carbon nanotube (MWCNT)/epoxy composites and neat epoxy under high strain-rate loading ( 10 5 – 10 6 s−1). The composites include randomly dispersed, 1 wt%, functionalized and pristine CNT/epoxy composites, as well as laminated, ∼50 wt% CNT buckypaper/epoxy composites. The pristine and functionalized CNT composites demonstrate spall strength and fracture toughness slightly higher and lower than that of neat epoxy, respectivel...
Abstract In this work, stress- and fracture mechanics-based criteria are developed to predict initiation and evolution, respectively, of intra- and inter-laminar cracking developed in composite laminates subjected to a relatively low energy impact (⩽15 J) with consideration of nonlinear shear behaviour. The damage model was implemented in the finite element (FE) code (Abaqus/Explicit) through a user-defined material subroutine (VUMAT). Delamination (or inter-laminar cracking) was modelled using ...
Abstract Progressive damage models based on continuum damage mechanics were used in combination with cohesive interface elements to predict the structural response and the failure mechanisms of composite laminates subjected to low-velocity impact. The potential of this simulation approach for correctly predicting the through-thickness distribution of internal damage was specifically examined in the study. The constitutive models for intralaminar and interlaminar damage modes were incorporated in...
Last. R.A. Shenoi(University of Southampton)H-Index: 34
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Composites are being widely used because of their high strength and stiffness, low density and high formability for creating complex shapes. An all-composite π joint is a structural connector known for its ability to reduce the weight and assembly cost while retaining a good load-carrying capability. Based on the material characteristics of unidirectional fiber composites used in composite π joints, a modified maximum stress failure criterion, which is able to assess damage onset, propagation an...
#1HX Hu(Anhui University of Science and Technology)
#2LM Meng(Anhui University of Science and Technology)
Last. CJ Wang(Anhui University of Science and Technology)
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To study the dynamic compression and tensile mechanical behaviors of a bicomponent epoxy resin matrix composites, which were filled with a semi-crystalline thermoplastic Polyether-ether ketone (PAE...
Abstract Delamination represents one of the most severe failure modes in composite laminates, especially when they are subjected to uniaxial compression loads. The evaluation of the delamination damage has always been an essential issue of composite laminates for durability and damage tolerance in engineering practice. Focusing on the most typical and representative elliptical delamination issue, an analytical model simultaneously considering the conservative buckling process and non-conservativ...
#2Ala Tabiei(UC: University of Cincinnati)H-Index: 22
Abstract null null The commonly used bilinear cohesive law doesn’t consider the effects of strain rate and plastic strain, but it is well known that strain rate and plastic strain can greatly affect materials’ mechanical response. In this paper a new bilinear cohesive law is proposed that can handle these two effects and enables reciprocating load. Compared with the commonly used bilinear cohesive law, one difference in the new bilinear cohesive law is that normal traction and tangential tractio...
Abstract An analytical model was developed for the prediction of small mass impact response including delamination effects in orthotropic composite plates, which mainly focuses on the relatively weak resistance of fiber reinforced polymer (FRP) laminates to small mass impact. Mode parameters of the delaminated structure obtained through perturbation-based dynamic analysis were substituted into the dynamic impact model. The alterations of the structural response caused by the occurrence of delami...
Abstract This paper investigates delamination mechanisms of composite laminates subjected to low-velocity impact. To obtain delamination data between plies with different fiber orientations, thermal-deply tests were conducted on quasi-isotropic laminates after low-velocity impact. Regularities of delamination positions in different interfaces as well as the matrix cracks distribution through the laminate thickness were analyzed. It is found that delamination positions are influenced by matrix cr...
The numerical prediction of impact-induced damage to composite materials and the subsequent residual strength under compression loading continue to be a challenging task. The current study proposes...
Abstract Automated Fiber Placement is currently being used to manufacture large and complex composite structures. However, the final composite products may include manufacturing defects such as gaps and overlaps, which may reduce the mechanical performance of the structure. The effect of these defects on the compression strength and also medium velocity impact loading with the impact energies of 15 J to 50 J have been experimentally investigated earlier. However, there is still a lack of knowled...
Last. Jianyu Zhang(Chongqing University)H-Index: 25
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Abstract Delamination of composite laminates under mode I loading is usually accompanied by large scale fiber bridging. Characterization of the bridging-traction law is of significant importance in delamination simulations to account for the effect of fiber bridging in such situation. This paper proposed a semi-analytical methodology to determine the bridging-traction law of composite laminates under mode I loading. The enhanced beam theory is physically improved by considering the bending-exten...
Abstract Through-thickness compressive stress of composite laminates can inhibit the interlaminar shear failure which has been proved by experiments. However, common delamination damage initiation criterion cannot well describe this mechanism. For this issue, in this article, based on the insight of the failure mechanism, an interlaminar failure function is constructed at first. Then, a delamination failure criterion considering the effect of through-thickness compression on interlaminar shear f...